1. Field of the Invention
The present invention relates to a battery pack controlling apparatus. In particular, the present invention relates to a battery pack controlling apparatus for detecting unusual heating of at least one of a number of cells or battery modules constituting a battery pack.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 10-270094 discloses an apparatus for detecting unusual heating of a battery. In accordance with the disclosed apparatus for detecting unusual heating of a battery, a temperature sensor whose electrical resistance rapidly increases with an increase in temperature is externally mounted to each one of a number of cells, and the resistance values of all such temperature sensors in series connection are measured, whereby unusual heating of the cells can be detected. The detection of unusual heating of the cells is necessary for security concerns.
However, the aforementioned apparatus for detecting unusual heating of a battery disclosed in Japanese Laid-Open Patent Publication No. 10-270094 requires that a temperature sensor be mounted to each one of a number of cells just for the sake of detection of unusual heating of the cells, and therefore is not cost efficient.
Moreover, this laid-open publication fails to mention controlling the input and/or output of the battery pack upon detection of unusual heating of a cell.
Since there are as many temperature sensors in series connection as there are cells, the resistance value of all of the temperature sensors for the entire battery pack is equal to a multiple of the resistance value of each temperature sensor by a factor of the number of cells.
Therefore, in order to enable detection of an unusual heating of any cell in such a manner that the unusual heating will not be obscured by the changing resistance of the entire battery pack responsive to temperature changes, it is necessary to employ temperature sensors whose resistance values exhibit a sharp change at a point of inflection.
If each cell experiences a relatively small increase in temperature, then the resistance value of the associated temperature sensor will not reach a point of inflection, so that the temperature increase will be obscured by the changing resistance of the temperature sensors of the entire battery pack. Therefore, it is impossible to achieve stepwise control of the input and/or output of each cell based on the detection of minute changes in the resistance of the cells.
According to the present invention, there is provided a battery pack controlling apparatus for controlling input to or output from a battery pack, wherein: the battery pack includes a plurality of blocks in series connection; and each of the plurality of blocks includes a plurality of batteries in series connection, the battery pack controlling apparatus including: a battery power input/output section for controlling input and output of battery power to and from the battery pack; a block voltage detection section for detecting a block voltage of each of the plurality of blocks; a battery current detection section for detecting a battery current of the battery pack; an unusual heating detection section for detecting unusual heating of at least one of the plurality of batteries based on the block voltage and the battery current; and a vehicle controlling section for controlling the battery power input/output section based on results of unusual heating detection by the unusual heating detection section, wherein the unusual heating detection section includes an internal resistance calculation section for calculating an internal resistance of each of the plurality of blocks based on the block voltage and the battery current, and wherein the unusual heating detection section detects unusual heating of the at least one of the plurality of batteries based on the internal resistance of each of the plurality of blocks and a predetermined threshold value.
In one embodiment of the invention, the battery pack controlling apparatus further includes a battery temperature detection section for detecting a battery temperature of the battery pack; the unusual heating detection section further includes a threshold value setting section for setting the predetermined threshold value based on the battery temperature of the battery pack; and the unusual heating detection section detects unusual heating of the at least one of the plurality of batteries based on the internal resistance of each of the plurality of blocks and the predetermined threshold value as set by the threshold value setting section.
In another embodiment of the invention, the vehicle controlling section controls the battery power input/output section in a stepwise manner based on results of unusual heating detection by the unusual heating detection section.
In still another embodiment of the invention, the unusual heating detection section further includes: a variance calculation section for calculating an average value and a variance "sgr"2 of the block voltages of the plurality of blocks; and a variance unusual heating detection section for detecting unusual rising of the internal resistance of the at least one of the plurality of batteries based on the block voltage of each of the plurality of blocks, the average value, and the variance "sgr"2, and wherein the vehicle controlling section controls the battery power input/output section based on results of unusual rising detection by the variance unusual heating detection section.
In still another embodiment of the invention, the variance unusual heating detection section determines unusual rising of the internal resistance of the at least one of the plurality of batteries when at least one of the block voltages is equal to or greater than a predetermined value at a time of charging or when at least one of the block voltages is equal to or smaller than a predetermined value at a time of discharging.
In still another embodiment of the invention, the variance calculation section calculates an average voltage difference value representing an average of voltage differences between the block voltage at a first time and the block voltage at a second time as well as a voltage difference variance representing a variance of the voltage differences, and the variance unusual heating detection section detects unusual rising of the internal resistance of the at least one of the plurality of batteries based on the voltage differences, the average voltage difference value, and the voltage difference variance.
In still another embodiment of the invention, the first time includes a point in time at which the battery current detected by the battery current detection section is substantially zero.
In still another embodiment of the invention, the unusual heating detection section includes a available capacity unusual heating detection section for detecting unusual rising of the internal resistance of the at least one of the plurality of batteries based on high available capacity diagnosis and low available capacity diagnosis for respective ones of the plurality of blocks, and the vehicle controlling section controls the battery power input/output section based on results of unusual rising detection by the available capacity unusual heating detection section.
Thus, the invention described herein makes possible the advantages of (1) providing an economical battery pack controlling apparatus which obviates the need for mounting a temperature sensor to each one of a number of cells; (2) providing a battery pack controlling apparatus which is capable of controlling the input and output of a battery pack responsive to an increase in the temperature of a cell, so as to prevent the cell from remaining in an abnormal condition; and (3) providing a battery pack controlling apparatus which is capable of controlling the increase in the temperature of cells, so that the entire battery pack can sustain a longer period of use.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.